I've found when I add more than a couple corals at a time [like monthly] ... I don't give the corals as much attention and often at least one suffers because of it [don't keep as close an eye as I can, or one becomes unglued, or I put the prettier coral in the visible spot - when another would probably best in those conditions.
I've not had bioload problems, but have lost a handful of frags that way - mainly through poor glue attachment [mostly Acropora] and just not noticing the first day or two they fell into the rockwork ...
After a month, they've grown onto the rockwork, or have stabilized and are acclimated to their conditions ...don't need as much attention [and having looked at them 100 times, I won't forget about one of the 5 new corals for a few days]